September 2, 2014

FLO Cycling - Tire Pressure

We get a lot of questions about the optimal tire pressure to use with FLO wheels. There are a couple of common misconceptions with regards to tire pressure.

120psi is the optimal pressure.

Higher tire pressures equate to lower rolling resistance and make you faster.

Let's talk briefly about those misconceptions.

120 PSI

I believe the 120psi misconception has trickled down over the years. I think it was a combination of narrower wheels, the pressure recommendation on the side of a tire, and word of mouth. Over the years the width of rims have changed and tires have changed as well.

Higher Pressures Make you Faster

Taken to extremes, this seems to make sense. If you ride down the road with a tire that has really low pressure, it's easy to see that this is much slower. Naturally, if low pressure is slow, then high pressure is fast, right? Actually, it is right, but only up to a certain point. If a tire has too much pressure, it actually, starts to bounce around on the small imperfections in the pavement. All of this bouncing wastes energy and makes you slower.

So what Should You Do?

There's a place somewhere in the middle where the correct amount of tire pressure limits the "slowness" created by too little pressure, and limits the bouncing you experience when you have too much pressure. Tom Anhalt, author of the blog Blather 'bout Bikes, has studied tire pressures and rolling resistance at length. When I have a question about rolling resistance and tire pressure he's my go-to guy. We've even shared wind tunnel data with Tom in the past to find the tire that has the optimal balance of rolling resistance and aerodynamics.

When I asked Tom about the optimal tire pressures for FLO wheels, he gave me the following dataset.

Note: Never exceed the maximum pressure recommended by your tire manufacturer AND never inflate to a pressure less than the minimum pressure recommended by your tire manufacturer. Riders over 180 lbs or 81kg are advised to inflate their tires to the maximum pressure recommended by their tire manufacturer without exceeding 150psi or 10bar. Riders less than 110 lbs or 50kg are advised to inflate their tires to the minimum pressure recommended by their tire manufacturer. The above data set is a modification of the data found here. The data was modified to adjust for the width of FLO rims.

So how do you use this table? Let give a couple of examples us the standard table.

Example #1

Rider Weight: 150lbs

Tire Size: 700 x 23c

Knowing you have a 700 x 23c tire, you will start by using the green line. Now find your weight - 150 lbs - on the Y axis and then move over to the right until you hit the green line. Next, draw a line straight down to the X axis. The value on the X axis in this case is about 100 psi. This is your recommended tire pressure.

Example #2

Rider Weight:170lbs

Tire Size:700 x 25c

Knowing you have a 700 x 25c tire, you will start by using the red line. Now find your weight - 170 lbs - on the Y axis and then move over to the right until you hit the red line. Next, draw a line straight down to the X axis. The value on the X axis in this case is about 95 psi. This is your recommended tire pressure.

I hope this article has been helpful. If you have any questions at all, please leave them in the comments section below.

The chart is only for the rider weight. The weight of the bike is not taken into account. The chart was produced using rider weight so that is what I used.

Regarding front vs. rear pressure. Some people find decreasing the pressure on the front tire by 5-10 psi helps but at that point it's really a personal preference. The values in the chart are a great place to start. If you feel the need to adjust a few psi here or there after riding your bike, you can certainly do that... but again, it comes down to a personal preference.

Thanks for posting this! One question: Put any 23mm tire on a Flo rim and it will measure much more than 23mm, more like 25-26mm. So which line in the chart do I use in this case? The red or the green one?

About air pressure,On the FLO 60's there is a label that says on item 2 that the pressure should be 80-105psi and on item 3, that failure to adhere to said pressure will void your warranty. I have the Clydesdale build and I tip the scales at 207lbs. My tires' max recommended psi is 120. You mention on the article that I should follow that guideline.

This is a modification of the data found here: http://oaksandspokes.com/wp-content/uploads/2013/09/pressurechart121405B.jpg

We have modified this data to be more accurate with our wider 24.4mm rims. I'd imagine most of todays "newer" wide rims would work well with our recommendations. If you have the older 19mm brake track rims, I'd suggest you use the data from the link above.

i actually don't understand your way: for example you recommand to inflate to 5,5bar for a 70kg rider, but what if the manufacturer says minimum 8bar (many does) ??? you can't tell us to believe your recommandations and theirs when there is so much difference between them

I can't really answer that question without knowing what tire you are using. This is because different tires, have different max values. Most tires have a maximum pressure listed on the side of the tire. I'd recommend looking at your tire to determine the maximum allowed pressure.

If that is the max pressure for your tire then that is where the optimal rolling resistance likely is. That said, there's a human element to this as well. If you prefer the handling/comfort of 90/100 PSI then by all means feel free to ride with those pressures.

I find it a bit strange that if I weight 180 my tire pressure should be 120psi (manufacturer's max), but if I drop 1/10th of a pound the chart shows a recommended pressure of ~98psi. FWIW, I'm fluctuate between 178-183 on a regular basis.

I'm assuming you are using a 25mm tire. If you were using a 23mm tire the difference would only be a few PSI. The chart is given as a guide but you are certainly able to experiment as you see fit. I wouldn't recommend anything above or below tire manufacturer recommendations.